1. Field of the Invention
This invention relates to vehicle lamps and more particularly to a reflective surface of a reflector of such a vehicle lamp.
2. Description of the Related Art
Vehicle lamps are generally fitted with light sources, reflectors and lenses. As shown in FIG. 12, however, the reflective surface 2a of a reflector 2 is formed with a paraboloid of revolution with a longitudinal axis passing through a light source 4 as a reference axis Ax in a conventional vehicle lamp so that a desired light distribution pattern may be formed by causing light from the light source 4 to be reflected from the reflective surface 2a in substantially parallel to the reference axis Ax and then causing the light to be deflected and diffused by lens steps 6s formed on a lens 6.
Nevertheless, there exist problems arising from making it not so easy to obtain a light distribution pattern with less nonuniformity in light since the formation of the light distribution pattern totally depends on the deflecting and diffusing control functions of the lens 6 and also rendering the lamp lacking a feeling of transparency to be less externally attractive as the curvature of each lens step 6s becomes relatively larger.
It is an object of the present invention made in the aforementioned situation which provides a vehicle lamp that makes available a light distribution pattern with less nonuniformity in light and looks externally attractive with a feeling of excellent transparency.
The shape of the reflective surface of a reflector according to the present invention has been so contrived as to accomplish the object above.
In this invention, a vehicle lamp according to the present invention comprises a light source and a reflector having a reflective surface, being defined as a first cross section and a second cross section, with a longitudinal axis passing through the light source as a reference axis, wherein said first cross section which is defined as at least one of the horizontal and vertical cross sections including the reference axis on the reflective surface is set to such a curved shape that a reflected light from the light source reflected on the reflective surface is focused closer to the reference axis in the first cross section; and said second cross section including an axis in an emitting direction of the reflected light at each of points on said first cross section, which is further defined as a cross section to be orthogonal to said first cross section, wherein said second cross section is set to such a curved shape that a reflected light from the light source is in substantially parallel to the axis in the emitting direction of the reflected light on said first cross section in a central reflective area near the reference axis, and is set to such a curved shape that a reflected light from the light source is focused closer to the axis in the emitting direction of the reflected light on said first cross section in peripheral reflective areas on both sides of the central reflective area
The curved shape forming the first cross section including the reference axis on the reflective surface is not limited to a specific one but may be set to any shape as long as it is usable for focusing and reflecting the light from the light source closer to the reference axis within the first cross section; may be, for example, an ellipse with the reference axis as the major axis or what is similar thereto.
With respect to the second cross section including the axis in the direction of emitting reflected light at each of the points on the first cross section on the reflective surface and crossing the first cross section at right angles, as its curved shape forming the second cross section in the central reflective area is intended to reflect the light from the light source in substantially parallel to the axis in the direction of emitting the reflected light it is substantially parabolic to be concrete. However, the shape is not limited to a specific one but may be set to any shape as long as each of the curved shapes forming the second cross section in the peripheral reflective area is usable for focusing and reflecting the light from the light source closer to the axis in the direction of emitting the reflected light; may be, for example, an ellipse with the reference axis as the major axis or what is similar thereto.
By the xe2x80x98peripheral reflective areaxe2x80x99 is meant that the areas located on the respective sides in the first cross sectional direction against the central reflective area. However, the xe2x80x98peripheral reflective areaxe2x80x99 located on both sides in the second cross sectional direction may be included against the central reflective area.
As shown in the arrangement above, according to the present invention, the shape of the first cross section including the reference axis on the reflective surface of the reflector is set to the curved shape for focusing and reflecting light from the light source closer to the reference axis within the first cross section, and a light distribution pattern diffusing in the first cross sectional direction (after being concentrated once) can be obtained from the light reflected from the reflector.
Further, according to the present invention, the shape of the second cross section including the axis in the direction of emitting reflected light at each of the points on the first cross section is set to the curved shape for reflecting the light from the light source in substantially parallel to the axis in the direction of emitting the reflected light in the central reflective area, and the shapes of the peripheral reflective areas on both sides of the central reflective area are respectively set to curved shapes for focusing and reflecting the light from the light source closer to the axis in the direction of emitting the reflected light. Consequently, the following effect will be obtainable.
More specifically, the light source is sized to some degree, whereby the reflected light in the central reflective area closer to the light source is irradiated forward and becomes an image greater than the reflected light in both the lateral peripheral reflective areas.
According to this embodiment of the invention, the second vertical cross sectional shape of the central reflective area is set to the curved shape so that reflected light in substantially parallel to the axis in the direction of emitting the reflected light may be obtained. Further, each of the vertical cross sectional shapes of both the lateral peripheral reflective areas is set to the curved shape so that reflected light focusing closer to the axis in the direction of emitting the reflected light may be obtained. In consequence, the light distribution pattern horizontally diffusing can be widened vertically up to a substantially fixed width over its whole width and this makes it possible to readily provide a substantially rectangular light distribution pattern for the whole reflective surface, the pattern greatly expanding in the first cross sectional direction rather than the second cross sectional direction.
With the light source and the reflector, the light distribution pattern with less nonuniformity in light can readily be obtained and the light distribution pattern or any similar one required for the lamp can also be obtained despite the fact that the lens is a see-through lens or any similar one.
Since the reflective surface is formed with a smooth curved surface, a feeling of excellent transparency is made available for the lamp from the curved surface together with the see-through lens or any similar one.
Thus, according to the present invention, a light distribution pattern with less nonuniformity in light can readily be obtained and a vehicle lamp having a feeling of excellent transparency as well as a good external appearance becomes also obtainable.
Moreover, according to the present invention, as the light from the light source excluding part of the reflective area is caused by the reflective surface to be focused and reflected closer to the axis in the direction of emitting the reflected fight, the utilizing solid angle can be increased in comparison with the conventional case where the reflective surface is formed into a paraboloid of revolution. Thus, the lamp efficiency is made improvable thereby.
The xe2x80x98first cross sectionxe2x80x99 above may be one of the horizontal and vertical cross sections including the reference axis and may be set in accordance with the shape of the lamp and the desired light distribution pattern. As one of embodiments in this invention, a substantially rectangular light distribution pattern greatly expanding in the horizontal direction can readily be obtained when the shape is set to the horizontal cross section, whereby the desired light distribution pattern of the lamp can also readily be formed.
Further, in the arrangement above, the curved shape of the first cross section is set so that the focusing degree of the reflected light closer to the reference axis may be increased as the distance from the reference axis increases, whereby it is possible to obtain a luminous intensity distribution is obtainable such that the brightness gradually decreases from the central portion to the peripheral portion within the first cross section.
Still further, in the arrangement above, the curved shape of each second cross section in the peripheral reflective area is set so that the focusing degree of the reflected light closer to the reference axis in the direction of emitting the reflected light may be increased as the distance between the reference axis and the second cross section increases whereby it is possible to obtain a luminous intensity distribution is obtainable such that the brightness gradually decreases from the central portion to the peripheral portion within the second cross section.